Several components in the CIR system may be used to understand and augment the user's query. These could include components for named entity recognition, co-reference resolution, query completion and query rewriting. If these are being carried out in conversational context, they could also make use of a state tracker that stores current and past requests and responses. If the component augments the query before retrieval, then it can be evaluated using the retrieval-based evaluation in the previous section. Using TREC CAsT data, several studies employed methods that combine the current query with previous queries, with the goal that the augmented query will yield improved search results [1]}, [2]}, [3]}. These methods for query expansion and query rewriting are described in more detail in Chapter , along with other methods that use recognition and resolution to better process the text of the query and the candidate answers.
